The present invention relates to multi-color printing and more particularly to a ribbon shifting mechanism which can be utilized with a printer of the type in which a printhead, together with a multi-color ribbon, is traversed along a paper-supporting platen.
Multi-color printing utilizing multi-color ribbons is, of course, not new per se. Two-color ribbons are quite typically utilized in ordinary typewriters and, increasingly, multi-color capability is being introduced into high speed computer data printers. Examples of the latter are illustrated in U.S. Pat. Nos. 4,073,371; 4,088,218; 4,111,293; and 4,236,839. A need has been perceived, however, for an improved method of color changing for use in printers of the type in which a printhead, together with its ribbon, is traversed along a paper-supporting platen. In particular, a need was felt to generate ribbon shifting motions within the carriage, independent of its position. In particular, it was desired that the color changing operation occurs as rapidly as possible so that color could be changed within a line, with as little delay as possible. In most prior art multi-color printers actually reaching the marketplace color changing was typically accomplished only at the ends of the line.
Among the several objects of the present invention may be noted the provision of a moving printhead type of printer utilizing a multi-color ribbon; the provision of such a printer in which color may be changed within a line; the provision of such a printer in which motion is coupled into a moving printhead carriage independent of the carriage position; the provision of such a printer which will change colors quite rapidly; the provision of such a printer which is highly reliable and which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.